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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

12319 results found.

  1. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  2. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  3. Fermi GRB 250711A: Global MASTER-Net observations report
  4. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  5. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  6. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  8. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  9. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  10. Fermi GRB 250708A: Global MASTER-Net observations report
  11. IceCube-250708A: Global MASTER-Net observations report
  12. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  13. EP250704a/GRB250704B : HCT optical and NIR upper limits
  14. IceCube-250706A: EP-FXT follow-up observations
  15. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  16. IceCube-250706A: Global MASTER-Net observations report
  17. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  18. GRB 250706B: Swift/UVOT Detection
  19. GRB 250706A: Swift/UVOT Upper Limits
  20. IceCube-250416A: DDOTI Optical Upper Limit
  21. IceCube-250706A: COLIBRÍ optical upper limits
  22. Swift GRB 250706A: Global MASTER-Net observations report
  23. GRB 250706A: JinShan optical upper limits
  24. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  25. GRB 250706A: GROWTH-India Telescope optical upper limit
  26. GRB 250706A: Swift detection of a burst
  27. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  28. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  29. GRB 250704B: Swift/UVOT Upper Limits
  30. GRB 250704A: Swift/UVOT Detection
  31. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  32. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  33. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  34. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  35. EP250704a / GRB250704B: Swift-XRT counterpart detection
  36. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  37. GRB 250704A: REM detection of the optical afterglow
  38. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  39. GRB 250702F: Swift/UVOT Detection
  40. Fermi GRB 250703A: Global MASTER-Net observations report
  41. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  42. GRB 250424A: VIRT Optical Upper Limit
  43. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  44. GRB 250703A: DDOTI Optical Upper Limit
  45. GRB 250702F: REM optical afterglow detection
  46. EP250702a: Global MASTER-Net observations report
  47. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  48. Fermi GRB 250702E: Global MASTER-Net observations report
  49. Fermi GRB 250702B: Global MASTER-Net observations report
  50. Fermi GRB 250702F: Global MASTER-Net observations report
  51. Fermi GRB 250702C: Global MASTER-Net observations report
  52. Swift GRB 250702F: Global MASTER-Net observations report
  53. Konus-Wind detection of GRB 250627A
  54. GRB 250628B: Swift-XRT observations
  55. GRB 250628B: SVOM/VT optical upper limit
  56. GRB 250628A: REM optical/NIR upper limits
  57. GRB 250628A: VLT/X-shooter upper limits
  58. GRB 250628A: Swift/UVOT Upper Limits
  59. Fermi GRB 250626A: Global MASTER-Net observations report
  60. Swift GRB 250628A: Global MASTER-Net observations report
  61. GRB 250628A: Swift detection of a burst
  62. GRB 250625A: SVOM/C-GFT upper limit in early phase
  63. GRB 250625A: Swift/UVOT Upper Limits
  64. GRB 250625A: OHP/T193 optical detection
  65. Swift GRB 250625A: Global MASTER-Net observations report
  66. GRB 250625A: NOT z-band upper limit
  67. Fermi GRB 250625A: Global MASTER-Net observations report
  68. GRB 250625A: Swift detection of a burst
  69. Fermi GRB 250624A: Global MASTER-Net observations report
  70. Fermi GRB 250623A: Global MASTER-Net observations report
  71. Fermi trigger No 772190032: Global MASTER-Net observations report
  72. Fermi GRB 250621A: Global MASTER-Net observations report
  73. Fermi trigger No 772128434: Global MASTER-Net observations report
  74. Fermi trigger No 772058337: Global MASTER-Net observations report
  75. GRB 250615A: Kilonova-Catcher optical upper limits
  76. Fermi GRB 250617A: Global MASTER-Net observations report
  77. GRB 250615A/EP250615a: FTW optical and NIR observations
  78. GRB 250617B: Swift/UVOT Detection
  79. GRB 250617B: NUTTelA-TAO early time optical observations
  80. Fermi trigger No 771886893: Global MASTER-Net observations report
  81. Swift GRB 250617B: Global MASTER-Net observations report
  82. GRB 250617B: GOTO optical upper limit
  83. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  84. EP#01709178975: Swift-XRT counterpart detection
  85. EP-WXT trigger 01709178975: GOTO optical upper limit
  86. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  87. GRB 250615A: COLIBRÍ optical upper limit
  88. GRB 250615A: DDOTI Optical Upper Limit
  89. GRB 250615A: Swift/UVOT Upper Limits
  90. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  91. sb25061207/SVOM: T120 OHP optical upper limit
  92. Fermi trigger No 771752663: Global MASTER-Net observations report
  93. Swift GRB 250615A: Global MASTER-Net observations report
  94. Fermi trigger No 771718064: Global MASTER-Net observations report
  95. sb25061207: Mephisto optical upper limits
  96. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  97. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. Fermi trigger No 771494087: Global MASTER-Net observations report
  99. sb25061218: Swift-XRT observations
  100. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope

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